Scope of Works: Let’s Clean was engaged to investigate chemical removal of paint layers at Carrara House back to a naked substrate. Saturated steam removal was also tested.
The condition of the paint in the areas selected for testing was somewhat cracked and occasionally peeling or missing in some places. There were various stains from dirt, rust, and biological growth. In some areas the painted surface was quite powdery, suggesting deterioration of the upper layers of paint.
Method:
1. Identify inconspicuous areas to test paint removal: a column, plinth, quoin, and wall were selected at the back of Carrara House.
2. Test areas with saturated steam removal.
3. Test areas with chemical removal. A total of five patches were created for each area:
a. 2 x Heritage No.1 applications and removals, over two days.
b. 1 x GreyGel application followed by 1 x Heritage No.1 application, over two days.
Steam cleaning was relatively ineffective in each of the four areas.
While it did appear to remove one or two layers of paint, the effort required to remove them was determined to be impractical to warrant further investigation. This is because chemical removal would still be required for the layers that weren’t removed by steam, and chemical removal would also get through those upper layers anyway.
Chemical removal:
The results of the various test patches indicated that two applications of paint stripper (that is, one application left overnight and then removed, followed by a second application and removal) yielded better results than one application, even if that single application was left on for a longer period.
The most successful of these was generally two Heritage No.1 applications. While GreyGel did remove upper layers of paint, allowing a subsequent Heritage No.1 application to dissolve underlying paint layers, it appears that Heritage No.1 was also able to penetrate the upper acrylic layers on its own, without the need for GreyGel to help reach the stone.
